The development of thyroid cancer is influenced by several factors. In this paper, the risk factors for thyroid cancer are organized into five areas through literature review: family history, radiation exposure, excessive and insufficient iodine intake, obesity and metabolic diseases, and other factors. Family history About 5% of thyroid cancer patients have a family history of the same type of thyroid cancer. Usually, among papillary cancers, familial non-myeloid thyroid cancer is the most common, accounting for about 6.2% to 10.5% of all papillary cancer incidences. Familial thyroid cancer usually has a worse prognosis than sporadically occurring thyroid cancer. Thyroid cancer is also seen in patients with certain genetic defects, such as papillary carcinoma in familial adenomatous polyposis, multiple endocrine adenoma type 2 and its subtype Gardner syndrome. Radiation Radiation is the only identified risk factor for thyroid cancer, such as the atomic bomb explosion, the Chernobyl nuclear meltdown in the former Soviet Union, the Fukushima nuclear meltdown in Japan, and other catastrophic events. There is also an association between exposure to diagnostic radiography in childhood and the development of thyroid cancer in adulthood, and a history of previous head and neck radiation exposure and the development of thyroid cancer. Excess and deficient iodine intake Both excess and deficient iodine may contribute to the high incidence of thyroid cancer. Excess iodine intake may be associated with the growth of papillary thyroid cancer, and iodine deficiency may be associated with the high incidence of follicular thyroid cancer. No statistical association was found between iodine intake in fortified foods and thyroid carcinogenesis. Obesity and metabolic diseases A meta-analysis of body mass index (BMI) showed an association between BMI and thyroid cancer incidence, and the results of a study by Xu (Xu) et al. were consistent with their findings. Kitahara et al. analyzed the relationship between height and BMI in 320,000 children between the ages of 7 and 13 years and their thyroid cancer in adulthood, and concluded that there was a correlation between BMI in childhood and the development of thyroid cancer in adulthood. A meta-analysis by Wolinski et al. showed that the risk of thyroid nodules as well as thyroid cancer was increased in patients with acromegaly compared to controls. It has been suggested that insulin resistance or hyperinsulinemia in obese individuals or patients with metabolic diseases can induce thyroid cancer. Other studies on the association between dietary factors and thyroid cancer have also reported that excessive intake of smoked and preserved seafood, fats, cheeses, and starches may increase the risk of thyroid cancer, but further studies are needed; studies on the association between female reproductive factors (such as the number of births, use of sex hormones, regularity of menstrual cycles, and menopausal status) and thyroid cancer have not found consistent findings.